FFA1/GPR40 is a Gi/Gq-coupled GPCR that is activated by free medium and long-chain fatty acids. FFA1 receptors are expressed in brain tissue and insulin-producing β Pancreatic islets (Briscoe et al., 2003). FFA1 receptors regulate insulin release from islets in response to long-chain fatty acids in the plasma (reviewed in Brown et al., 2005). Cloned human FFA1 receptor-expressing ChemiBrite cells were made by stable transfection of HEK293 cells with ChemiBrite clytin and the FFA1 receptor. These stability-tested cells are ready for luminescent and fluorescent analysis of agonists, antagonists and modulators at the FFA1 receptor.